Ultrasonic couplant compositions and method for employing same

Abstract

Biodegradable water washable composition in the form of a gel for use in non-destructive ultrasonic inspection of surface and subsurface flaws and discontinuities in bodies, and which is stable and heat resistant, such composition consisting essentially of a (1) a surfactant comprised of certain straight chain, primary, aliphatic oxyalkylated alcohols, particularly biodegradable surfactants comprised of the nonionic condensation products of linear aliphatic alcohols having from 10 to 18 carbon atoms, with ethylene oxide and propylene oxide, preferably in the form of a mixture thereof, such as the material marketed as Plurafac A-24, or in the form of certain ethoxylated secondary alcohols, particularly the biodegradable nonionic surfactants comprised of ethoxylates of a mixture of secondary alcohols having linear alkyl chains of from 11 to 15 carbon atoms, and (2) silica, particularly fumed silica, such silica employed e.g. in a proportion of about 15% by weight of the composition. The composition or gel is applied to a surface of a body such as a metal aircraft structural part, and a probe or transducer of an ultrasonic testing device is contacted or pressed against the gel, and the transducer is caused to move or slide in various directions on the gel to transmit ultrasonic energy through the gel and the object, to inspect the object and locate any surface or subsurface flaws or discontinuities.